Source apportionment and wet deposition of atmospheric poly- and per-fluoroalkyl substances in a metropolitan city centre of southwest China

Sixty rainwater samples were collected covering four seasons from July 2020 to April 2021 from the center of Chongqing, a metropolitan city of southwest China, using automatic deposition sampler. The samples were analysed for 17 targeted poly- and per-fluoroalkyl substances (PFASs) by HPLC-MS/MS. The concentration of PFASs ranged from 3.31 ng/L to 196.14 ng/L and dominated by perfluoro-n-octanoic acid (PFOA), perfluoro-n-hexanoic acid (PFHxA), perfluoro-n-butanoic acid (PFBA) and sodium perfluoro-1-octanesulfonate (PFOS). The seasonal variations of dissolved and particulate PFAS were distinct, with the highest level in summer and autumn, respectively. Positive matrix factorization (PMF) and a wet deposition model were performed to apportion the sources and estimate the wet deposition flux of the 17 PFASs, respectively. PMF analysis indicated that, based on yearly average, paper packaging production (37.4%) and aqueous film forming foam (AFFF) usage (29.8%) were the two major sources, followed by textile production (16.7%) and electronic product manufacturing (16.1%). The highest source contributor for PFASs in winter was AFFF usage (47.0%); while in the other three seasons, it was paper packaging production that contributed the most (50.1%, 39.8% and 34.8% respectively). Seasonal average wet deposition flux of PFASs was estimated to be 13.9 ng/m2/day. The dry deposition of PFASs was estimated to account for 15.8% of the total atmospheric deposition flux, suggesting a more important role for wet deposition. The results of this study provide important information for understanding of PFASs occurrence and atmospheric wet deposition in Chongqing, and other urban centers across China.